A floating gate field-effect transistor (FET) is typically a planar transistor having a floating gate situated over a channel and a control gate situated over the floating gate. The floating gate is electrically insulated from the control gate and the channel, and charge may be stored in the floating gate. Fowler-Nordheim tunneling and hot-carrier injection are two approaches that can be utilized to modify the amount of charge stored in the floating gate. The charge stored in the floating gate can remain even when there is no power being applied to the floating gate FET.
Floating gate FETs have been utilized in various applications. As one example, floating gate FETs have been utilized as digital storage elements in erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM) and flash memory. As other examples, floating gate FETs have been utilized as neuronal computational elements in neural networks, analog storage elements, electronic potentiometers, and single-transistor digital-to-analog converters (DACs).